SONARJAVA-6824: Inline sameNullableTree to fix SonarQube always-false condition findings

Inline the null checks for enclosingExpression() directly in sameNewClass
so SonarQube can properly track nullability from the @nullable return type.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: romainbrenguier

java-checks/src/main/java/org/sonar/java/checks/TernaryOperatorSameOperationCheck.java

@@ -113,17 +113,15 @@ private static boolean sameNewClass(NewClassTree left, NewClassTree right) {
     if (left.classBody() != null || right.classBody() != null) {
       return false;
     }
-    return sameNullableTree(left.enclosingExpression(), right.enclosingExpression());
-  }
-
-  private static boolean sameNullableTree(Tree left, Tree right) {
-    if (left == null && right == null) {
+    var leftEnclosing = left.enclosingExpression();
+    var rightEnclosing = right.enclosingExpression();
+    if (leftEnclosing == null && rightEnclosing == null) {
       return true;
     }
-    if (left == null || right == null) {
+    if (leftEnclosing == null || rightEnclosing == null) {
       return false;
     }
-    return sameTree(left, right);
+    return sameTree(leftEnclosing, rightEnclosing);
   }
 
   private static boolean hasExactlyOneArgumentDifference(List<? extends ExpressionTree> leftArgs, List<? extends ExpressionTree> rightArgs) {